Solve the Equation and Express the Solution in Exact Form $$\log _ { 4 } \left( \log _ { 4 } x \right) = 1$$

Multiple Choice

Solve the equation and express the solution in exact form.
- $$\log _ { 4 } \left( \log _ { 4 } x \right) = 1$$

A) $\{ 256 \}$
B) $\{ 8 \}$
C) $\{ 16 \}$
D) $\{ 4 \}$